Carbonate formation mechanism in paleosol sediments of the Bohai Sea coastal zone,China

The Bohai Sea coastal zone of China consists of the Pacific Ocean to the east and Eurasia to the west; hence, this region is influenced by both the ocean and continental landmasses. The carbonate formation mechanism of eolian sediment within this area is poorly understood. The loess-paleosol sediments of the Miaodao stratigraphical section (MDS) contain a record of carbonate changes in this region during the last interglacial period. New insights into regional carbonate formation mechanisms since the last interglacial period were obtained by analyzing the ages of various sedimentary facies in combination with proxy paleoclimatic indices (including average grain size, standard deviation, CaCO₃ content, and clay minerals), as well as via foraminiferal analysis. The results led to three principal findings: (1) The carbonate content change in the MDS was neither controlled by grain size nor affected by minerals. The carbonate change controlled by precipitate leaching in the Loess Plateau region cannot explain the eolian sediments within the Bohai Sea coastal zone. (2) Various subsections contain obvious carbonate content changes caused by foraminiferal deposits atop the eolian sediments, which were deposited by storm surges during a high sea-level period. This increased the carbonate content in the eolian sediments and restricted the carbonate content in the Bohai Sea coastal zone. (3) Newly detected foraminifera of the last interglacial period on the eolian sediment of the MDS were the main source of carbonate content, providing a new understanding of the carbonate formation mechanism in eolian sediments different from that of the Loess Plateau.     

Distribution and speciation of heavy metals in surface sediments from the Yangtze estuary and coastal areas

The concentrations and speciation of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the sediments of the nearshore area, river channel and coastal zones of the Yangtze estuary, China, were systematically investigated in this study. The concentrations of all heavy metals except Ni in the sediments of the nearshore area were higher than those of the river channel and coastal zones. In the nearshore area, the concentrations of most heavy metals except Hg in the sediments of the southern branch were higher than those of the northern branch because of the import of pollutants from the urban and industrial activities around. When compared with the threshold effect level (TEL) and geochemical background levels, Cr, Ni and As accumulated and posed potential adverse biological effects. The speciation analysis suggested that Cd, Pb and Zn in the sediments of the three zones showed higher bioavailability than the other heavy metals, and thus posed ecological risk. Significant correlations were observed among Cr, Cu, Ni and Zn (r > 0.77) in the nearshore area, Ni, Cu, Zn and Pb (r > 0.85) in the river channel and Ni, Cu, Cr, Pb and Zn (r > 0.75) in the coastal zone. Principal component analysis (PCA) indicated that the discharge of unban and industrial sewage, shipping pollution and the properties of the sediments (contents of Fe, Mn, Al, TOC, clay and silt) dominated the distribution of heavy metal in the nearshore area, river channel and coastal zones of the Yangtze estuary.     

南通近海潮滩表层沉积物重金属含量特征与生态风险评价

基于南通近海(洋口港—吕四)潮滩特点布设潮滩断面并采集表层沉积物,根据样品汞、镉、铅、砷、铬等7种重金属元素含量测试结果,分析研究区沿海潮滩表层沉积物主要重金属元素含量特征,并与江苏其他滨岸地区潮滩沉积物的重金属含量进行对比,初步探讨2009—2012年南通沿海滩涂表层沉积物重金属含量变化与元素的相关性。采用潜在生态危害指数法评价南通近海潮滩表层沉积物中7种重金属元素的潜在生态危害系数及潜在生态风险。南通潮滩表层沉积物重金属含量分布均匀,且低于江苏省苏北其他地区沿海潮滩的沉积物含量。7种重金属元素的相关分析表明,Cu与Pb、Zn具有较好的相关性,Pb与Cd、Hg的相关性最差。潜在生态危害指数法评价表明,南通近岸潮滩表层沉积物7种重金属潜在生态危害系数均属低生态危害范畴,近岸海域(洋口港—吕四段)潮滩表层沉积物环境质量总体较好。     

Competitive adsorption,release and speciation of heavy metals in the Yellow River sediments,China

The competitive adsorption and the release of selected heavy metals and their speciation distribution before and after adsorption in the Yellow River sediments are discussed. The adsorption of metals onto sediments increases with increasing pH value and decreases with increasing ionic strength. The competitive coefficient K _c and the distribution coefficient K _d are obtained to analyze the competitive abilities of selected heavy metals, which are ranked as Pb > Cu >> Zn > Cd. The competition among selected heavy metals becomes more impetuous with increasing ion concentration in water. Speciation analysis was done by an improved analytical procedure involving five steps of sequential extraction. Cu, Pb and Zn were mainly transformed into the carbonate-bound form (50.8–87.7%) in adsorption. Most of (60.7–77.3%) Cd was transformed into the exchangeable form, and the percentage of carbonate-bound Cd was 19.7–30.4%. The release reaction was so quick that the release capacity of selected heavy metals from sediments to aqueous solution reached half of the maximum value only in 30 s. As opposed to adsorption, the release capacities of selected heavy metals were ranked as Cd > Zn >> Cu > Pb. In this study, Cd produces the most severe environmental hazards, because its concentration in the release solution is 85.8 times more than the human health criteria of US EPA.     

A geochemical study of long-chain n-aldehydes in Washington coastal sediments

A series of n-aldehydes, C₂₀ to C₃₂, with strong even-to-odd carbon preference was identified in the mixture of solvent extractable lipids isolated from various Washington coastal sediments. A limited survey of the lipid composition of surface waxes of foliage and cuticular waxes of pollen from several major plant species indigenous to the Pacific Northwest revealed that similar series of n-aldehydes are intrinsic to regional vegetation. Debris from such plants, discharged at the mouth of the Columbia River, represents a “preformed” source of the n-aldehyde series accumulating in sediments from the Washington coastal region. Although the evidence suggests n-aldehydes are largely introduced erosionally to this region as a chemical component of land-derived debris and are not formed in situ in the coastal sediments, further study is warranted to establish the postdepositional stability of this series of compounds relative to other lipids of higher plantwax origin. Despite but few literature reports of the occurrence of these geochemicals, long-chain n-aldehydes are very likely common in many sediments from environments that receive an input of detrital organic matter from higher plants.     

Geochemical assessment and speciation of metals in sediments of Osun and Erinle Rivers,Southwestern Nigeria

Fifty sediment samples were collected from Osun (urban) and Erinle (suburban) rivers in addition to ten samples of the underlying rock types (schist and gneiss) and analyzed for elemental constituents while speciation of metals was determined by sequential analysis. Data were geochemically evaluated and ArcGIS was used to generate geochemical maps. Metal concentrations (ppm) in sub-urban and urban areas were Cd (0.2–0.2, 0.2–1.1), Cu (37.0–272.0, 49.0–970.0), Ni (6.0–27.0, 3.0–43.0), Pb (16.0–67.0, 15.0–2650.0), Zn (32.0–170.0, 50.0–987.0), Co (8.0–60.0, 2.0–86.0), Cr (26.0–153.0, 9.0–128.0), V (30.0–142.0, 9.0–135.0), and Mn (442.0–5100.0, 107.0–3930.0), respectively. In the rocks, Cu, Ni, Pb, Co, Cr, V, and Zn, concentrations (ppm) were below detection limit (BDL)-0.05, BDL-38.00; 6.23–12.00, BDL-20.00; 3.78–6.23, BDL-5.00; BDL-0.20, BDL-4.00; 5.00–9.00, BDL-66.00; 15.99–32.00, BDL-130.00; and 18.00–26.00, BDL-48.00, respectively, with Cu, Pb, Zn, Cd, and Mn of elevated concentrations in sediments compared with that of the rocks, being indication of additional anthropogenic sourcing. Calculated contamination indices revealed contamination for sediment from the urban areas compared to those from the sub-urban. High percentage of Pb (2.94–81.92%), Cu (31.69–45.95%), Zn (49.2–65.5%), Cd (31.69–45.95%), and Mn (12.13–37.50%) are hosted by the bio-available phases (carbonate, organic, and sulfide). The geochemical distribution of metals in the sediments of the Osun and Erinle rivers is governed by both geogenic (Ni-Cr-Co-V) and anthropogenic (Pb-Cd-Zn) activities. Elevated concentration and occurrences of the selected metals in the bio-available phases pose potential health risk to people in the urban area.     

Polycyclic aromatic hydrocarbons in surface sediments of Laizhou Bay,Bohai Sea,China

Concentration, distribution, and sources of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments of Laizhou Bay, China. Total PAH concentrations ranged from 97.2 to 204.8 ng/g, with a mean of 148.4 ng/g. High concentrations of PAHs were found in the fine-grained sediments on both sides of the Yellow River estuary (YRE). In contrast, low levels of PAHs were observed in relatively coarse grain sediments, suggesting hydrodynamics influence the accumulation of sedimentary PAHs. The YRE and its adjacent area is the main sink for Yellow River-derived PAHs. Both PAH isomer ratios and principal component analysis (PCA) with multivariate linear regression (MLR) were applied to apportion sources of PAHs. Results indicated that both pyrogenic and petrogenic PAH sources were important. Further PCA/MLR analysis showed that the contributions of coal combustion, petroleum combustion and a combined source of spilled oil and biomass burning were 41, 15 and 44%, respectively. From an ecotoxicological viewpoint, the studied area appears to have low levels of PAH pollution.     

The distribution and risk assessment of heavy metals in water,sediments, and fish of Chaohu Lake,China

In this study, the concentrations of seven heavy metals (As, Cd, Cu, Cr, Ni, Pb, and Zn) in the water, sediments, and nine tissues of eight fish species in Chaohu Lake were detected. And the ecological risk of sediments and food safety caused by heavy metals were evaluated. The mean concentrations of metals (As: 8.21, Cd: 0.58, Cu: 2.56, Cr: 0.50, Ni: 26.47, Pb: 3.51, Zn: 23.05 μg/L) in the water were found lower than the threshold values for the first-grade water quality (China environmental quality standards for surface water). The mean concentrations of Cr, Cu, Ni, Pb, and Zn in the sediments were 41.79, 19.31, 7.61, 7.09, and 102.85 μg/g, respectively, while the concentration of As and Cd was recorded below the detection limit. The ecological risk assessment demonstrated that metals in the sediments posed low ecological risk. The bioaccumulation of metals in fish tissues showed relatively high concentrations in liver, brain, kidney, and intestines while low levels of metals were detected in muscle. A fascinating phenomenon was firstly noticed that all metals highly existed in fish brain and exhibited an especially significant positive correlation with the metal concentrations in sediment, indicating a health risk for Chinese due to their consumption favor of fish head.     

A multi-method approach for the study of lanthanum speciation in coastal and estuarine sediments

Two independent analytical methods (sequential extraction and kinetic extraction methods) were applied in order to understand the distribution and speciation of La in the coastal and estuarine sediments from the central east coast of India. Sequential extraction study revealed that La was primarily present as inert complexes (~ 50–60% of the total La) in all the sediments. Amounts of ~ 20–30% of the total La in all the sediments were found to associate with the total organic carbon (TOC) in the sediments. The dissociation rate constants of La–sediment complexes obtained from kinetic extraction studies revealed that the concentration of thermodynamically weak complexes of La gradually increased with the increasing La/TOC ratio in the sediments.     

Magnetic signature of heavy metals pollution of sediments: case study from the East Lake in Wuhan,China

Detailed magnetic measurements and geochemical analyses were performed on 114 sediment samples collected from the East Lake, Wuhan city, China, to establish a possible link between the enhanced concentration of anthropogenic magnetic particles and heavy metals with known sources. Relatively higher magnetic susceptibility values (mass-specific, χ, >150 × 10⁻⁸ m³ kg⁻¹) were observed for samples near the pollution sources: e.g. the Wuhan Iron and Steel Company (WISC), the Qingshan Thermal Power Plant (QTPP), the banks (driveways) of the lake and near the sightseeing route of yachts on the lake. Moreover, χ is positively correlated to the concentration of Pb (correlation coefficient r = 0.682), but negatively or weakly correlated with both Zn and Cu. In contrast, anhysteretic remanent magnetization (ARM) is significantly correlated with these major heavy metals (r = 0.645 for Zn–ARM, 0.699 for Pb–ARM and 0.841 for Cu–ARM, respectively), which indicate that ARM serves a better indicator for the pollution of heavy metals in this lake. Thermomagnetic analysis combined with magnetic hysteresis measurements revealed that magnetites in the pseudo-single-domain/multidomain grain-size regions are dominant. Scanning electron microscopy and energy dispersive X-ray examinations of the magnetic extracts showed that these Fe-rich particles have different morphologies: orange-peel structure, hollow structure with adhered smaller particles, Zr-rich melted-like irregular particles, pear-shaped spherules and spherules with slick surfaces. These features are typical for particles produced by anthropogenic activities. Because of the genetic relationship between the environmental setting of the East Lake and the nearby pollution sources, this study suggests that in situ magnetic surveys are sensitive to evaluate the environmental pollution on the lake bottom.     

Anthropogenic impacts on reduced inorganic sulfur and heavy metals in coastal surface sediments, north Yellow Sea

This study investigated the organic carbon, reduced inorganic sulfur, and heavy metal distribution in superficial sediments at an estuary, a wastewater discharge area, and a mariculture area, as compared with an unpolluted distal site, in the north Yellow Sea, China. Sediment grain size, acid volatile sulfur (AVS), chromium (II)-reducible sulfur, elemental sulfur, total sulfur, total organic carbon (TOC), total nitrogen and trace metal content were determined for each site. These results indicate that pollution leads to increased TOC at all affected sites, which in turn leads to elevated AVS. The resultant change in diagenetic environment leads to changes in the mineralogical fate of Mn. Pb, Zn, Cu, and Cd: all are present at elevated concentrations, and with more metal in the non-residual fractions. Cd shows by far the most elevated concentrations and most significant increase in non-residual fractions and consequently poses the most significant pollution risk.     

The effect of grain size on the Cu, Pb, Ni, Cd speciation and distribution in sediments: a case study of Dongping Lake, China

This paper examines the surface sediments collected from Dongping Lake in China for speciation and distribution of toxic heavy metals (Cu, Pb, Ni, Cd) in different grain size fractions, and for the factors that need to be considered in potential hazard of metals to the environment. Four grain size fractions (<63, 63–78, 78–163 and 163–280 μm), divided in wet condition, and bulk samples less than 280 μm in diameter were analyzed for their distribution, density and appearance. A three-stage extraction procedure following the BCR protocol was used to chemically fractionate metals into “acid soluble”, “reducible”, “oxidizable” and “residual” fractions. Correlation analysis was used to analyze the datasets. The results showed that <63 μm grain size part constitutes the major proportion of the sediments, but its density is the smallest among the four grain size fractions. In general, the metal content curve against grain size presents “S” distribution, and the highest concentrations do not exist in <63 μm grain size. Appearance observation indicates that the adsorbed substance increases gradually along with the decreasing grain size. The dominant speciation of elements and the extent of pollution are responsible for the metal distribution in different grain size sediments. While studying bioavailability and mobilization of metals, it is advisable to take metal speciation, grain size distribution and density into consideration.     

Flood risk assessment in a coastal lagoon under present and future scenarios: Ria de Aveiro case study

Iranian strong motion records as well as detailed conditions of their instrument sites and the characteristics of their causative seismic sources are compiled and processed. The dataset consists of 2286 three-component records from 461 Iranian earthquakes with at least two high-quality records having moment magnitude from 3.9 to 7.3. These records are about 20% of the Iranian database and are suitable for seismic hazard analysis and engineering applications. Perhaps for the first time in the literature, the distance to the surface projection of the fault is reported for a great number of records corresponding to earthquakes with M > 6.0. The raw accelerations are processed using the wavelet de-noising method. Having corrected and filtered these raw data, the pseudospectral accelerations are calculated for each of the three components of time series, separately. In addition to the ground motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record is also developed. Moreover, careful revision of the characteristics of the earthquakes such as location, magnitude, style of faulting and fault rupture plane geometry, if available, is carried out using the best available information in a scientifically sound manner. Finally, we also focus on special ground motion records including records with peak ground acceleration (PGA) >300 cm/s² and distances less than 30 km. These are “exceptional” records in the Iranian dataset and include less than 2% of the selected dataset.     

Mobility and ecological risk assessment of heavy metals in surface sediments of Xiamen Bay and its adjacent areas,China

Xiamen Bay (XMB) has received substantial loadings of pollutants from industrial and municipal wastewater discharged since the 1980s. To assess ecological risks and the current spatial changes of metal contaminants in bottom surface sediments, 12 samples were collected. Samples were subjected to a total digestion technique and analyzed by ICP–OES for Cu, Pb, Zn, Cr, and Cd, and by AFS for Hg and As. Among these metals, Zn had the highest values (68–268 mg kg⁻¹), followed by Pb (27–71 mg kg⁻¹), and lower concentrations were found for Cd (42–1,913 μg kg⁻¹) and Hg (0–442 μg kg⁻¹). In comparison with the average crustal abundance values, the results indicated that nearly half of the sediment samples of XMB and its adjacent areas were contaminated by Cd, Pb, Zn, and As. Furthermore, based on the modified BCR sequential extraction procedure, the chemical speciation of heavy metals (Cd, Cr, Cu, Pb, Zn, Hg, and As) in selected sediment samples were evaluated in this study. Data from BCR sequential extractions indicated that Cd posed a medium ecological risk, whereas, Cr posed low risk since its exchangeable and carbonate fractions were below 4%, and the mobility of heavy metals in XMB decreased in the order Cd > Pb > Cu > Zn > Hg > As > Cr. By applying mean effects range median quotients (mERMQ), the results showed that Yuandang Lagoon with mERMQ value >0.5 would be expected to have the greatest potential toxic risk in amphipod within XMB and its adjacent areas.     

福建泉州湾近岸海域沉积物重金属来源分析与生态风险评价

【研究目的】 受重金属含量影响,泉州湾表层沉积物环境质量面临巨大生态风险,然而重金属含量影响因素及潜在来源研究相对薄弱。【研究方法】 通过采集泉州湾近岸海域表层沉积物样品,以元素含量及粒度分析归纳出重金属分布特征、富集程度为基础,使用Hakanson生态风险指数法识别湾内沉积物潜在生态风险程度,并进一步通过正定矩阵因子分解法及主成分分析,定量分析不同重金属主要来源。【研究结果】 在晋江与洛阳江交汇处出现沉积物粒度低值区,易于重金属富集,表层沉积物重金属富集程度为Hg>As>Cd>Pb>Zn>Cu>Cr>Ni。湾内沉积物整体处于中度生态风险状态,Cd对生态风险贡献程度最高（37.90%）,其次为Hg（29.38%）。Cr与Ni主要源于母岩风化,Cu与Zn、Pb受母岩风化影响及矿山冶炼的共同影响,Cd与As分别主要源自近岸污水排放与燃料燃烧,而Hg的来源较为复杂。研究区表层重金属主要来源依次为矿山冶炼、母岩风化、污水排放以及燃料燃烧,贡献率依次为33.95%,31.16%,22.26%与12.21%。【结论】 陆域物质随地表径流的输送对泉州湾表层沉积物生态环境质量造成了巨大风险,未来需要特别加强对不同介质中Hg的归趋及环境行为研究。     

典型内陆湖泊沉积物氮、磷和重金属分布特征及生态风险评价——以武汉市武湖为例

城市内陆型湖泊湿地对城市生态系统具有重要的作用。以武汉市武湖为例,采用数理统计、营养盐指数、地累积指数和潜在生态风险指数等方法,对武湖表层沉积物中的氮、磷、有机质和重金属的平面分布特征、影响因素、富集污染程度、生态风险进行评价。结果表明: 武湖西北部表层沉积物中总氮、总磷和有机质的含量明显高于东南部,武湖周边地表径流和农田是营养元素的主要来源,旱地较水田有利于沉积物中总磷的富集; 武湖沉积物中有机质为内源水生植物和外源陆生植物的混合来源,与总氮具显著正相关关系; 沉积物中重金属含量总体较低,局部呈现高镉,平面上总体北部高于南部; 沉积物中重金属富集程度和潜在风险较低,局部地区镉和铅为轻微富集,镉和汞具中等潜在风险; 沉积物的潜在生态风险为低至中等,潜在生态风险与沉积物中镉的分布高度一致。     

A geochemical study of the forms of metals present in sediments from Spencer Gulf,South Australia

Metal contaminated sediments and live shells from near-shore sites and from tidal flats adjacent to the lead-zinc smelter at Port Pirie were collected for study. Some samples were separated into size fractions and density sub-fraction and the density separates examined with the electron microprobe for Zn, Pb, Cd, S, Mg, Ca, Fe, Si, Al and other elements. Some samples were examined whole. Correlations between the elements, and particularly between Zn, Pb and sulphide sulphur (as distinct from sulphate sulphur) were tested. It was found, for example, that very fine precipitated ZnS was present at contaminated sites in Spencer Gulf, where it occurred in clay-carbonate aggregates, in the magnesian calcite of shell fragments, and in fragments of decaying seagrass. On the other hand, Zn and Pb sulphides were rarely found in the tidal flats, where the metals were associated with fine-grained dolomite in the sediment.